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Патент USA US3095371

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June 2s, 1963
M. D. STONE
.
3,095,361
METHOD OF MANUFACTURING TINPLATE
Filed Feb. 27, 1961
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3,095,361
Patented June 25, 1963
1
the strip in its ultra-thin and soft condition; in which
connection when cognizance is taken of the intricacies of
the equipment that performs this manner of processing
Morris D. Stone, Pittsburgh, Pa., assignor to United Engi
of the very thin strip, it will really be understood why
neering and Foundry Company, Pittsburgh, Pa., a cer
poration of Pennsylvania
great scrap losses are involved. Moreover, in this pro
cedure it has been found that the strip could only be
Filed Feb. 27, 1961, Ser. No. 91,708
rolled to the thin desired gauges by overloading the con
3 Claims. (Cl. Zim-_28)
ventional 5~stand tandem cold mill, or by using a 6-stand
This invention relates to a method of producing very
mill, or alternately by a second succeeding separate roll
thin tinplate characterized by a high production capacity 10 ing step. In this connection, it is to be pointed out that
and ‘capable of producing tinplate at a substantial saving
the maximum hardness that has been found practical to
in manufacturing costs over known methods and where
achieve in this method has fallen within the range of
in the tinplate will have improved metallurgical charac
-6 (T-30 Rockwell of 67 to 73).
teristics.
With respect to the second procedure currently being
This economic and metallurgical advancement in the
used in an attempt to produce ultra-thin tinplate, in order
production of tinplate is realized by practicing a method
to minimize the necessity of handling, transferring and
in which the parent strip is reduced to an ultra-thin gauge
processing the strip in its ultra-thin and soft condition,
thereby affording a considerable savings in cost of ma
the procedure is essentially as follows:
terial, equipment and labor as may be required for pro
The -hot rolled strip in this case is reduced to approxi
3,095,361
METHOD OF MANUFACTURING TINPLATE _
ducing the tinplate, as well as a marked reduction in scrap 20 mateiy the order of .020 inch thicker than in the case
losses, while, at the same time, yielding a product having
of the previous explained method, ie., approximately
improved hardness and strength characteristics.
of the order of .100 inch thick. The hot rolled and
pickled strip is transferred to a tandem cold reducing
mill where the strip is reduced to a thickness of the order
In view of the fact that normal gauge tinplate, which
falls within the ranges .007 to .011 inch, is not econom
ically suitable for all phases of the container market, the 25 of .009 inch, that is, approximately double its final de
ability of tinplate to maintain and to continue to improve
sired thickness. After the cold reduction operation, the
its position in this market depends to an appreciable ex
strip is transferred in its still relatively thick gauge to
tent on whether ultra-thin tinplate can be produced more
an annealing line, where it is cleaned and annealed in
the usual manner. From the annealing line, the strip,
the economical manufacture of very thin tinplate has 30 still in its relatively thick but now soft state, may then
to do with whether the tinplate will have the requisite
be processed in a skin-passing mill, although, in some
physical properties to enable it to serve its intended pur
cases, this step may not be included. The strip is then
pose. Two other major problems have to do with the
transferred to a thinning line, where it is cleaned, pickled,
additional equipment necessary to produce such tinplate
tinned, reñowed, passivated or chemically treated and
and the considerable scrap losses incident thereto. These 35 oiled. After tinning, the strip is then reduced about 50%
economically. One lof the major problems confronting
scrap losses are brought labout as :a result of the thin strip
in a second cold reduction mill to the iinal desired ultra
being damaged during the many processing, handling and
thin gauge and having the desired hardness. The degrees
transferring steps which are involved in the production of
of hardnesses that are known to be obtained in this method
the tinplate. Because of the magnitude of these problems,
have been lwithin the range of T~7 (T-30 Rockwell of
it has been questioned by some skilled in the art whether 40 7l to 78). After the rolling of the tinned strip, it is
very thin tinplate can be economically produced.
transferred in its ultra-thin condition to a fourth process
In order to better understand the uniqueness and nov
line and to its sixth independent processing step where
elty of the present invention, an understanding of the
it is cleaned and passivated, and sometimes reflowed for
present-day commercial attempts at producing very thin
the second time.
tinplate is believed necessary. At present, there are but 45
In this second procedure, while it has the advantage
two such procedures for making available in limited
that the thin product in its soft condition is involved in
amounts ultra-thin tinplate lfor use in the manufacture of
less handling than in the first procedure, it will be appre
containers.
ciated that to obtain this advantage a substantial increase
One procedure is to utilize the `ordinary processing
in equipment and labor force is necessary. Moreover,
equipment employed to produce normal gauge tinplate, 50 in view of the `fact that the tinned strip is subjected to
which consists of reducing the hot rolled and pickled strip
a rolling operation in which the surface of the strip may
in a tandem cold reduction rolling mill where the strip
become marred, it is necessary to perform a second reilow
is reduced immediately to its ultra-thin gauge, i.e., to
operation as well as a chemical treatment and a second
an order of .0045" thick. This `operation is followed by
cleaning operation. it goes without saying that such an
a continuous annealing process, wherein the ultra-thin
overall process results in increased cost of manufacturing
strip is cleaned and annealed to a soft metallurgical con
the tinplate.
'
dition. Thereafter, the strip, which is not only very
it
is
the
principal
object
of
the
present
invention to
thin but also very soft, both of which factors being con
provide a method of manufacturing tinplate that will
ducive to high scrap losses, is transferred to a skin-pass
rolling mill for further processing. This operation is de 60 be ultra-thin and of low cost, that will keep to a mini
signed primarily to develop the desired mechanical prop
mum the scrap losses incident to the production thereof,
erties, along with achieving a smoother and flatter strip
that will require no additional equipment and labor force
surface. The strip, however, retains a considerable de
over the first method described above and Still consider
gree of softness after the skin-.pass operation.
ably less with respect to the second aforementioned
Subsequent to this skin-pass operation, the ultra-thin
65
strip is transferred for the third time to an electrolytic
tinning line. In the tinning line, the strip is ñrst cleaned,
pickled and tinned, after which it is passed through re
ilowing, passivating or chemical treatment and oiling
zones. In this procedure, it is to be appreciated that it 70
is necessary to repeatedly handle, transfer and process
method, and yet will have the advantage `of a high pardo
duction capacity which will not involve additional clean
ing, reflowing or chemical 4treating operations to produce
tinplate having Ia maximum of hardness and strength as
imparted by cold rolling.
This object and the other novel features of the present
invention will be more fully appreciated when the fol
3,095,361
'a
«a
its final reduction to its ultra-thin form in the reduction
mill Z3 in which the thickness should be within the range
of .003 to .006 inch. In this regard, it is important to
FIG.`1 illustrates diagrammatically and in sequence
point out that in order to achieve the full advantage of
the novel steps of the present invention.
this invention, the reduction taken in the -rnill 23 should
As will be apparent to those skilled in the art, the vari
be of the order of from 30 to 60 percent. For the pur
ous processing units illustrated in FIG. l and described
pose of the description of the present invention, it will
hereinafter employed in the herein disclosed rnethod are
be »assumed that the final thickness of the strip will be
in themselves well-known elements in the manufacture
of the order of .0045 inch, which will represent a 50
of steel strip as exemplified in The Making, Shaping and
Treating of Steel, United States Steel, 7th edition.
10 percent reduction. As mentioned previously, a substan
tial savings in the overall cost of producing the tinplate
With reference t0 FIG. l there is shown the last mill
is thus realized in reducing the thickness of the strip
stand of a hot strip rolling mill 11 wherein the hot strip is
to Such an extent. It is one of the features of this in
reduced in thickness and following which it is coiled on
vention to provide a method wherein such tinplate, re
a mandrel 12. In order to realize the full «advantages of
lowing description thereof is read in light of the drawing
in which;
the present invention it is recommended that the strip
be reduced in the hot rolling imill to a gauge within the
range of .080 to .110 inch thick. For the purpose of
sulting from the practice thereof, will have this charac
teristic. In this connection, it is to be appreciated that
not only is the mill 23 employed at this particular stage
of the operation to reduce the strip to its final thickness
describing the present invention, it will be assumed that
prior to tinning, but just as important and of equal sig
the thickness of the strip issuing from the hot mill is
of the order of .100 inch. The hot rolled strip, in the 20 nificance is the fact that the reduction taken within the
previously mentioned range will impart a substantial
form of a coil, is transferred from the mandrel 12 to a
hardness to the strip and, in addition, will improve its
pickling line 13 in which it is, in the usual manner, placed
strength qualities. It is ya feature of the invention herein
on a pay-off reel 14, joined to the end of a previous strip
«disclosed that the strip will be given a hardness of the
and fed through the pickling zones, after which it is
order of T-6 to T-S (T-3O Rockwell of 67 to 83) and
coiled again on a wind-up reel 15. Of course, the strip
that this hardness will be achieved primarily by rolling.
during the pickling operation is still in a very thick
It will be appreciated that this degree of hardness will
condition, Ii.e., as previously mentioned .100 inch, so
enable the tinplate to be used for the intended purpose,
that there will be experienced no scrap losses such as
notwithstanding its extreme thinness.
would result if very thin strip were being pickled.
From the pickling line, the pickled strip in coiled form, 30
is transferred to a tandem cold reduction mill 16 where
the coil is placed on a pay-off reel 17, fed through each
of the five, or »as shown in phantom six, stands of the
mill and then wound on a tension reel 18. Acconding
to the teachings of the present invention, the strip will
be reduced in the cold reduction mill to a thickness with
After the second cold reduction operation the strip, in
coil form, is transferred in its very thin but very hard
condition to an electrolytic thinning line 26 where it is
placed on a pay-olf reel 27, joined to the trailing end
of a previous strip, and fed through the line, after which
it will be coiled upon a windup reel 28. This electrolytic
tinning line incorporates the usual equipment adapted
in the range of .006 to .012 inch. For the purpose of
this description, it will be assumed that the thickness of
to electro-clean, pickle, tin, reñow, passivate and oil the
experiencing the considerable scrap losses that are in
herent in handling very thin material,
After the cold reduction mill operation, the relatively
further transferring, handling and processing of the
»and the leading end joined to the trailing end of `a pre
vious istrip, »and fed through the annealing line. As is
customary, the strip will be cleaned before being an
nealed lafter which it will pass through the annealing 55
the present invention provides a method wherein the
resulting tinplate is made very thin with a substantial
reduction in the material cost and in the practice of
strip. It is a feature of this invention to perform all
rolling of the strip prior to the tinning operation there
the strip issuing from the cold mill »16 is of the order
of .009 inch. This thickness represents approximately 40 by avoiding the possibility of marring the tinned sur
faces. To accomplish this object, the strip, according
double the desired final thickness of the product. In
to the present invention, Will be presented to the thin
this condition, it is to be observed that the strip will
ning line in its ñnal very thin gauge. However, since
be still relatively thick and by reason of the rolling op
by employing the method of the present invention, the
eration very hard. In view of the fact that the strip’s
strip will have a substantial hardness and improved
thickness -is approximately twice as ‘great as its ultimate
»desired gauge, the handling, transferring and the immed 45 strength qualities obtained by cold rolling of the strip
and as a result scrap losses Iwill be minimized in the
iate subsequent processing thereof will lbe done without
strip.
In summarizing the advantages of the present invention
thick hard strip, in coil form, is transferred to an an 50 over the prior procedures Áfor attempting to produce
tinplate more economically, it will be appreciated that
nealing line ¿19‘ where it is placed on a pay-off reel 21
zone and be coiled on a windup rcel 22.
It is to be
which substantially all of the transferring, handling and
processing of the strip are performed, while 4the strip
is still in its soft thick condition. Furthermore, when
the strip is in its very thin condition, which is only
for a small fraction of the overall processing and han
in view of this fact in the further handling, transferring 60 dling time, this strip is maintained very hard so that
a considerable reduction in the scrap losses over the
and processing thereof, scrap losses will be minimized.
appreciated that at this stage of the operation the strip,
as it leaves the «annealing line, will be very soft, but at
the same time it will have a substantial thickness, and
Following the :annealing operation, the strip -in coiled
entire processing operation is effected. In addition, the
form, is transferred to :a second cold reduction mill 23
strip not only will be characterized by a substantial
which may consist of either one or two or more stands,
hardness and improved strength qualities, which are
a second stand being shown in phantom in the draw 65 achieved by rolling, but the strip after tinning will not
ing. In this operation the strip, in coiled form, is
he subjected to any rolling, thereby resulting in an over
adapted to be placed on a pay-off reel 24, fed through
all advantage that not only is the product economically
the mill and wound upon a tension reel 25. As pointed
produced but it is produced on a line having a very high
out above, the strip when it is transferred .from the an
nealing line and during the time it is being handled at 70 capacity.
In accordance with the provisions of the patent statutes,
the entry side of the second reduction mill 23 will be
I
have
explained the principle and operation of my in
in a soft condition, but at the same time it will be rela
vention and have illustrated and described what I con
tively thick, hence minimizing scrap losses during this
sider to represent the best embodiment thereof. How
phase of the operation. According to the teaching of
the present invention, the strip is adapted to be giVeIl 75 ever, I desire to have it understood that within the scope
3,095,361
6
of the appended claims, the invention may be practiced
otherwise than as specifically illustrated and described.
and continuously electrolytically tinning the strip in
the thin hard condition.
I claim:
3. In a method of producing very thin tinplate char
1. In a method of producing tinplate characterized
acterized by the fact that when the strip is in a metal
Áby a high degree of hardness suitable for use in the 5 lurgically soft condition, it is maintained relatively thick,
manufacture of containers, the steps including:
and when in its very thin condition the strip is metal
lurgically very hard, where-by in both conditions the
strip lends itself to ready handling, transferring and
cold reducing the strip to a thickness of at least .006
inch and thicker;
annealing such strip;
processing with minimum losses due to breakage, bend
cold reducing the annealed strip by an amount of 10 ing, tearing and the like, and further characterized by
at least 3() percent and »greater yto impart to the strip
the fact that all of the rolling processes are performed
a hardness of at least T-5,
prior to the tinning of the strip, the steps including:
and electrolytically tinning the strip in its thin hard
cold reducing the strip to a gauge of at least .006
condition.
inch and greater which will be relatively thick as
2. In a method of producing tinplate suitable for use 15
compared with the desired final gauge thereof;
in the manufacture of containers in a minimum number
continuously annealing the strip while in its rela
of processing steps and in a manner that scrap losses will
tively thick condition;
be substantially reduced and the strip will be character
ized by a high degree of hardness achieved by rolling,
the steps including:
reducing this strip in a hot rolling mill to a thickness
-between the lower and upper limits of .080 to .110
cold reducing the soft annealed relatively thick strip
20
inch, respectively;
further reducing the cold strip in a cold rolling mill
to a thickness between the lower and upper limits 25
of .006 to .012 inch, respectively;
annealing said strip as cold reduced;
cold reducing the annealed strip by an amount be
tween the lower and upper limits of 30 to 60 per
cent, respectively to impart to the strip a hardness 30
between the lower and upper limits of T-6 to T-S,
respectively,
at least 30% and greater to its final thin gauge to
impart a substantial hardness and strength to the
strip,
and as a final step tinning the strip in its thin hard
condition.
References Cited in the file of this patent
UNITED STATES PATENTS
2,673,836
2,906,652
Vouada ____________ _.- Mar. 30, 1954
Kiefer ______________ _.. Sept. 29, 1959
1520,373
472,120
Australia ____________ __ Sept. 27, 1945
Canada _____________ _.- Mar. 13, 19511
FOREIGN PATENTS
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